In motor vehicle chassis, the wheel suspensions, via which the wheels are connected to the basic structure, are usually a spring as well as a shock absorber. In this context, different possibilities are known as regards the construction of the spring (coil springs, leaf springs, torsion springs) as well as its spatial arrangement relative to the other components of the wheel suspension, especially relative to the associated shock absorber. A variant that is widely used, especially for steerable (front) wheels, is so-called MacPherson struts, in which a shock absorber is disposed within a spring constructed as a coil spring. In contrast, especially for non-steerable (rear) wheels, wheel suspensions in which a shock absorber is disposed outside a spring constructed as a coil spring can be found to a considerable extent.
It is further known that motor vehicles can be equipped with a height-positioning device, in order that, if necessary, the ground clearance can be increased (e.g. for driving onto ramps or the like) or the basic structure can be lowered (e.g. for fuel economy during highway driving). Typically, although not imperatively, this height-positioning device engages in one of the foot points of the spring of the wheel suspension in question and changes this, although in principle it is not decisive whether the spring foot point associated with the basic structure or else with the wheel in question is positioned. Besides pneumatic and electrical spring-foot-point positioning drives (see, for example, DE 102007051971 B4 and DE 102007051299 A1), hydraulic spring-foot-point positioning drives in particular are known, for example from DE 3223195 A1, DE 102009047100 A1, US 5181696 A, EP 2301773 A1, JP 2010-149550 A and WO 2014/142160 A1 as well as from DE 19744757 A1. In this connection, a hydraulic cylinder-piston arrangement associated with the respective wheel suspension is pressurized in controlled manner by a hydraulic aggregate. In the process, and to this extent deviating from the preamble of claim 1, a common central hydraulic aggregate may be provided for several wheel suspensions, as is the case for the motor vehicle chassis disclosed in DE 19744757 A1, for example, or else several decentralized hydraulic aggregates associated with the respective wheel suspension may be provided, which respectively pressurize only one single hydraulic cylinder-piston arrangement.
A motor vehicle chassis of the class in question, corresponding to the preamble of claim 1, is known from DE 102005010098 A1. In this case, a linear actuator, acting on the upper spring foot point and constructed as a cylinder-piston arrangement, is disposed within the spring. This piston is constructed as a hollow piston, within which the motor-pump unit as well as a storage chamber for hydraulic fluid are disposed. The pump of the motor-pump unit then defines, together with the annular end face of the hollow piston, the effective end area of the piston. For pressurization of the hydraulic working chamber constructed in the cylinder at the end upstream from the piston, hydraulic fluid is displaced by means of the motor-pump unit out of the storage container into the working chamber.
In view of the prior art mentioned in the foregoing, the present invention is directed toward providing a motor vehicle chassis of the type mentioned in the introduction, which, as regards the possibility of actively changing the height of the basic structure above the roadway, is characterized by a previously unknown suitability in practice. In particular, the intention is to provide a motor vehicle chassis with an especially compact and nevertheless reliably operating height-positioning device.